Expanding Universe

It is a remarkable fact that all galaxies are receding away from us. If we discount the possibility that we on Earth occupy a special place in the Universe, this means that the Universe must be expanding. This can be pictured in the raisin bread dough analogy:

 

Figure 15.3: Expanding Raisin Bread

In this picture, as the dough rises, each raisin becomes further and further from all the other raisins. No one raisin occupies a special spot in the dough in this context. It is thought that the Universe is expanding the same way, in that all points are becoming further and further away from each other.